Dual-mode power amplifier with switchable working power and mode switch method

ABSTRACT

The invention discloses a dual-mode power amplifier with switchable working power and a mode switch method. The power amplifier adopts a multi-tap input transformer, and realizes the switching between preload line and output load line by controlling the on/off of the intermediate switch connected with taps, so as to achieve the best power conversion efficiency under different maximum output powers. By using the change-over switch to control the capacitance value of the matching capacitor, it is easier to adjust the load line, thus further ensuring the performance of the power amplifier provided by the invention. The intermediate switch and change-over switch are integrated on an independent chip by CMOS/phemt/bihemt/SeGe/SOI, etc, or on a power amplifier chip by CMOS/phemt/bihemt/SeGe/SOI, etc, which is easy to realize.

TECHNICAL FIELD

The invention relates to a power amplifier and a mode switch method, inparticular to a dual-mode power amplifier with switchable working powerand a mode switch method.

BACKGROUND

Power amplifier is a device that can amplify the voltage or power ofinput signal, which consists of electronic tube or transistor, powertransformer and other electrical components. It is widely used incommunication, broadcasting, radar, television, automatic control andother devices.

Two main performance indexes of power amplifier are output power andpower conversion efficiency. For most commonly used power amplifiercategories(A/B/C/D/E/F/F⁻¹, etc.), the optimal power conversionefficiency corresponds to the maximum output power, when the outputpower is lower, its power conversion efficiency will also decrease.Therefore, the conventional single power amplifier is difficult toachieve high power conversion efficiency under different output powers.

Since the maximum output power of power amplifier and its correspondingoptimal power conversion efficiency are determined by the load line ofthe power amplifier, in order to achieve high power conversionefficiency under different output powers, a number of groups of poweramplifiers can be integrated in the system. Each group of poweramplifiers adopts different load lines and corresponds to differentmaximum output powers. When the system works, the corresponding poweramplifiers can be turned on according to power requirements. Thedisadvantage of this method is that it requires to integrate two or moregroups of power amplifiers in a limited space, which not only increasesthe manufacturing/material cost, but also is difficult to realize inengineering applications.

SUMMARY

In order to solve the problems existing in the prior art, one of thepurposes of the present invention is to provide a dual-mode poweramplifier with switchable working power, which can realize switchingbetween preload line and output load line, and further realize maximumoutput power switching.

In order to achieve the purpose of the present invention, the dual-modepower amplifier with switchable working power provided herein includes:

an input transformer, comprising a plurality of output taps, and aninput coil is loaded with a to-be-amplified signal;

an output transformer, comprising a plurality of input taps, the numberof the input taps is matched with that of the output taps of the inputtransformer, and an output coil amplified signals;

an intermediate switch and a power-amplifier transistor, the pluralityof output taps of the input transformer are connected with the inputtaps of the output transformer via the intermediate switch and thepower-amplifier transistor, the intermediate switch is configured with acontrol signal to conduct the power-amplifier transistor connected inseries with the intermediate switch, so that one or more of the outputtaps of the input transformer are communicated with the input taps ofthe output transformer, and an amplified signal is output after beingtransformed by the output transformer; and a first matching capacitorand a second matching capacitor, the first matching capacitor and thesecond matching capacitor are connected in parallel between taps at bothends of the input coil of the output transformer and ground.

Furthermore, a change-over switch is connected between taps at both endsof the input coil of the output transformer and the first matchingcapacitor.

Furthermore, two or more of the intermediate switches and thechange-over switches are a group, integrated on a single SOI chip, or apower amplifier chip.

Furthermore, two or more of the intermediate switches are a group,integrated on a single SOI chip, or a power amplifier chip.

Furthermore, the dual-mode power amplifier with switchable working powerfurther includes an input matching circuit and a preamplifier, whereinthe to-be-amplified signal loaded on the input coil of the inputtransformer is matched by the input matching circuit and amplified bythe preamplifier and then loaded.

Furthermore, the input matching circuit includes an input filtercircuit.

Furthermore, the dual-mode power amplifier with switchable working poweralso includes an output matching circuit, wherein the amplified signaloutput by the output coil of the output transformer is output afterpassing through the output matching circuit.

Furthermore, the output matching circuit includes an output filtercircuit and a switch group, and the amplified signal output by theoutput coil of the output transformer is filtered by the output filtercircuit, then loaded on the switch group and output via the switchgroup.

Furthermore, the dual-mode power amplifier with switchable working powerfurther includes a selection circuit mainly composed of a selectionswitch S and a capacitor C, and the selection circuit is connected inseries between taps at both ends of the input coil of the outputtransformer. Through the selection circuit, certain two groups of tapsin the input coil of the output transformer can be selected to conductaccording to specific conditions, so as to form high-power conduction,low-power disconnection, or high-power disconnection and low-powerconduction.

Beneficial effects: the power amplifier provided by the invention adoptsmulti-tap input transformer, and realizes the switching between thepreload line and output load line by controlling the on/off of theintermediate switch connected with the taps, so that the power amplifierconstitutes different working states to achieve the best performanceunder different maximum output powers.

A change-over switch is used to control the capacitance value of thematching capacitor and adjust the load line of the output stage, thusfurther ensuring the performance of the power amplifier provided by theinvention.

The intermediate switch and change-over switch are integrated on anindependent chip by the process of CMOS/phemt/bihemt/SeGe/SOI, etc, oron a power amplifier chip by the process of CMOS/phemt/bihemt/SeGe/SOI,etc, which is easy to realize.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a functional block diagram of the power amplifier provided bythe present invention;

FIG. 2 is a schematic circuit diagram of the power amplifier provided bythe present invention;

FIG. 3 is a schematic circuit diagram of the bias circuit described inthe present invention;

FIG. 4 is a schematic circuit diagram of the output matching circuitdescribed in the present invention;

FIG. 5 is an another schematic circuit diagram of the output matchingcircuit described in the present invention;

FIG. 6 is an another schematic circuit diagram of the output matchingcircuit described in the present invention;

FIG. 7 is an another schematic circuit diagram of the output matchingcircuit described in the present invention;

FIG. 8 is an another schematic circuit diagram of the output matchingcircuit described in the present invention;

FIG. 9 is an another schematic circuit diagram of the output matchingcircuit described in the present invention;

FIG. 10 is an another schematic circuit diagram of the output matchingcircuit described in the present invention;

FIG. 11 is an another schematic circuit diagram of the output matchingcircuit described in the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The technical solution claimed in the present application will befurther described in detail with reference to the drawings and specificembodiments.

The technical solution claimed by the present application is a dual-modepower amplifier with switchable working power and a mode switch methodbased on the power amplifier, wherein the functional block diagram ofthe dual-mode power amplifier with switchable working power is shown inFIG. 1, which includes:

an input transformer T1, including a plurality of output taps, and aninput coil is loaded with a to-be-amplified signal;

an output transformer T2, including a plurality of input taps, thenumber of the input taps is matched with that of the output taps of theinput transformer, and an output coil amplified signals;

an intermediate switch and a power-amplifier transistor, the pluralityof output taps of the input transformer are connected with the inputtaps of the output transformer through the intermediate switch and thepower-amplifier transistor, the intermediate switch is configured with acontrol signal to conduct the power-amplifier transistor connected inseries with the intermediate switch, so that one or more of the outputtaps of the input transformer are communicated with the input taps ofthe output transformer, and an amplified signal is output after beingtransformed by the output transformer; and a first matching capacitorand a second matching capacitor, the first matching capacitor and thesecond matching capacitor are connected in parallel between taps at bothends of the input coil of the output transformer and ground.

The number of output taps of the input transform, and the number ofinput taps of the output transformer in the power amplifier can be 2, 4,6 or other. The described power amplifier can be either a field effecttransistor or a triode transistor. Here, the power amplifier disclosedby the present invention is further introduced by taking the examplethat the input and output transformers are configured with 4 taps andthe power-amplifier transistor is a field effect transistor, as shown inFIG. 2. The output coil of the input transformer T1 includes tap 1, tap2, tap 3 and tap 4, and the input coil of the matched output transformerT2 includes tap 5, tap 6, tap 7 and tap 8. Tap 1 is connected to thebase of power amplifier Q1 via intermediate switch S1 and capacitor C1.The collector of power amplifier Q1 is connected to tap 5, and theemitter is grounded. Tap 2 is connected to the base of power amplifierQ2 via intermediate switch S2 and capacitor C2. The collector of poweramplifier Q2 is connected to tap 6, and the emitter is grounded. Tap 3is connected to the base of power amplifier Q3 via intermediate switchS3 and capacitor C3. The collector of power amplifier Q3 is connected totap 7, and the emitter is grounded. Tap 4 is connected to the base ofpower amplifier Q4 via intermediate switch S4 and capacitor C4. Thecollector of power amplifier Q4 is connected to tap 8 and the emitter isgrounded. Tap 5 and tap 8 are grounded via a first matching capacitor C5and a second matching capacitor C6, respectively, which constitute aparallel connection.

One end of the input coil of input transformer T1 is connected to thepower supply VCC1 and grounded via capacitor C9, and the other end isloaded with the signal to be amplified. The conduction of intermediateswitches S1-S4 is controlled by external control signals. One end of theoutput coil of output transformer T2 is grounded, and the other endoutputs an amplified signal.

The working state of the power amplifier provided by the invention iscategorized as Class E power amplifier working state and Class F⁻¹ poweramplifier working state. The input coil of input transformer T1 isloaded with a signal to be amplified, and a control signal is loaded onintermediate switches S1-S4 to make intermediate switches S1 and S4conduct or intermediate switches S2 and S3 conduct. When intermediateswitches S1 and S4 are turned on, power amplifier Q1 and Q4 are turnedon, and the signal to be amplified is loaded on taps 5 and 8 of theinput coil of output transformer T2. The load line consists of firstmatching capacitor C5 and output transformer T2, in this state, thepower amplifier is in Class E power amplifier working state.

When intermediate switches S2 and S3 are turned on by the loaded controlsignal, power amplifiers Q2 and Q3 are turned on, and the signal to beamplified is loaded on taps 6 and 7 of the input coil of outputtransformer T2. The load line forms a 3rd order harmonic impedance bysecond matching capacitor C6 shown in the solid lined box of FIG. 2, theinductance between taps 5 and 6 shown in the solid lined box of FIG. 2,and the inductance between taps 7 and 8 shown in the solid lined box ofFIG. 2. In this state, the power amplifier is in Class F⁻¹ poweramplifier working state.

In order to better adjust the load line of the power amplifier, achange-over switch S5 and a change-over switch S6 are added on the basisof the above solution. Change-over switch S5 is connected in seriesbetween tap 1 and first matching capacitor C5, and change-over switch S6is connected in series between tap 8 and first matching capacitor C5.The conduction of change-over switch S5 and change-over switch S6 iscontrolled by an external control signal, and the capacitance value ofthe matching capacitor can be controlled by the change-over switch.

In addition, the dual-mode power amplifier provided by the inventionfurther includes a selection circuit mainly composed of a selectionswitch S and a capacitor C, and the selection circuit is connected inseries between taps at both ends of the input coil of the outputtransformer.

In order to make the power amplifier amplify the signal voltage withoutdistortion, the power amplifier provided by the present invention alsoincludes a bias circuit, the schematic diagram of the bias circuit isshown in FIG. 3, which includes bias branches with the same number asthe power amplifier, each bias branch includes an output end, and theoutput control signal is loaded on the control end of the poweramplifier. Each bias branch includes a switch transistor T1, a resistorR1, a resistor R2, a resistor R3, a capacitor C7, a diode D1 and a diodeD2. The power supply end of the switch transistor T1 is connected withan external control signal (such as a power supply) via resistor R1, andresistor R2 is connected with the output end of switch transistor T1.The control end of switch transistor T1 is grounded via capacitor C7,switch transistor T1 is also connected to the anode of diode D1, thecathode of diode D1 is connected to the anode of diode D2, and thecathode of diode D2 is grounded. The control end of switch transistor T1is also connected with an external control signal via resistor R3.Switch transistor T1 may be a triode transistor or a field effecttransistor.

In order to ensure the stability of the signal loaded on inputtransformer T1, the power amplifier further includes an input matchingcircuit for filtering the to-be-amplified signal and a preamplifier Q5.The input matching circuit includes an input filter circuit, and theinput filter circuit can be any of the existing capacitance filtercircuit, inductance filter circuit, RC filter circuit or LC filtercircuit. The input filter circuit used here includes a capacitor C8, acapacitor C10 and an inductor L1. The first plate of capacitor C8 isused as an input end for loading signals, and the second plate ofcapacitor C8 is connected to the control end of preamplifier Q5 viacapacitor C10. The second plate of capacitor C8 is further grounded viainductor L1, and the power supply end of preamplifier Q5 is grounded,the output end is connected to the input coil of input transformer T1.The preamplifier Q5 may be a triode transistor or a field effecttransistor.

To obtain the bandwidth and harmonic suppression required by the poweramplifier, the power amplifier further includes an output matchingcircuit for filtering the signal output by output transformer T2, whichincludes an output filter circuit and a switch group composed of severalswitches. The output filter circuit may consist of a capacitor and aninductor, and any one of the following may be obtained.

1. A low-pass filter circuit, its circuit connection is shown in FIG. 4.It includes a capacitor C11, a capacitor C12, an inductor L2 and aninductor L3. One end of inductor L2 is an input end connected to theoutput coil of output transformer T2, and the other end is connected tothe switch group via inductor L3. The end of inductor L2 connected toinductor L3 is grounded via capacitor C11, and the end of inductor L3connected to the switch group is grounded via capacitor C12.

2. A high-pass & low-pass circuit, its circuit connection is shown inFIG. 5. It includes a capacitor C13, an inductor L4, an inductor L5 anda capacitor C14. The first plate of capacitor C13 is an input endconnected to the output coil of output transformer T2, and the secondplate is connected to the switch group via inductor L5. The second plateof capacitor C13 is grounded via inductor L4, and the end of inductor L5connected with the switch group is grounded via capacitor C14.

3. A low-pass trap circuit, its circuit connection is shown in FIG. 6.It includes a capacitor C15, a capacitor C16, an inductor L6, inductorL7, inductor L8 and inductor L9. One end of inductor L6 is an input endconnected to the output coil of output transformer T2, and the other endis connected to the switch group via inductor L7. The end of inductor L6connected to inductor L7 is grounded via capacitor C15 and inductor L8,and the end of inductor L7 connected to the switch group is grounded viacapacitor C16 and inductor L9.

4. A high-pass & low-pass trap circuit, its circuit connection is shownin FIG. 7, it includes an inductor L10, inductor L11, inductor L12, acapacitor C17 and a capacitor C18. One end of capacitor C17 is an inputend connected to the output coil of output transformer T2, and the otherend is connected to the switch group via inductor L11. The end ofcapacitor C17 connected to inductor L11 is grounded via inductor L10,and the end of inductor L11 connected to the switch group is groundedvia inductor L12 and capacitor C18.

The switch groups described in the above four types of filter circuitsmay consist of 4, 6, 8 or other numbers of switches. In the presentapplication, the switches S7-S11 are used, and each switch is used asone output, and its on-off is controlled by an external control signal.The switches of the switch group may be integrated on a single chip, andthe process technology can be selected from SOI/CMOS/PHEMT/BIHEMT/SeGe,etc.

In addition to the above structures, the output matching circuitdescribed in the present application can be one of the followingstructures:

A. As shown in FIG. 8, the output matching circuit includes an inductorL13, inductor L14, inductor L15, inductor L16, inductor L17, inductorL18, a capacitor C19, capacitor C20, capacitor C21, a switch group A,switch group B, an independent switch S12 and independent switch S13.One end of inductor L13 is an input end connected to the output coil ofoutput transformer T2, and the other end is connected to switch group Aand switch group B via inductor L15 and inductor L16 respectively. Theend of inductor L13 connected to inductor L15 and inductor L16 isfurther grounded via capacitor C19 and inductor L14. Switch group A isfurther grounded via independent switch S12, capacitor C20 and inductorL17, and switch group B is further grounded via independent switch S13,capacitor C21 and inductor L18. Switch group A and Switch group Bconsist of several switches controlled by external control signals, eachswitch serves as one output, and independent switch S12 and independentswitch S13 are controlled by external control signals.

B. As shown in FIG. 9, the output matching circuit includes a capacitorC29, an inductor L14, inductor L15, inductor L16, inductor L17, inductorL18, a capacitor C20, capacitor C21, a switch group A, switch group B,an independent switch S12 and independent switch S13. The first plate ofcapacitor C29 is an input end connected to the output coil of outputtransformer T2, and the second plate is connected to switch group A andswitch group B via inductor L15 and inductor L16 respectively. Thesecond plate of capacitor C29 is further grounded via inductor L14.Switch group A is further grounded via independent switch S12, capacitorC20 and inductor L17, and switch group B is further grounded viaindependent switch S13, capacitor C21 and inductor L18. Switch group Aand Switch group B consist of several switches controlled by externalcontrol signals, each switch serves as one output, and independentswitch S12 and independent switch S13 are controlled by external controlsignals.

C. As shown in FIG. 10, it includes capacitors C22-C26, inductor L19,switch group A, switch group B, independent switch S12 and independentswitch S13. The first plate of capacitor C12 is an input end connectedto the output coil of output transformer T2, and the other end isconnected to switch group A and switch group B via capacitor C23 andcapacitor C24 respectively. The end of the capacitor C22 connected tocapacitor C23 and capacitor C24 is further grounded via inductor L19.Switch group A is further grounded via independent switch S12 andcapacitor C25, and switch group B is further grounded via independentswitch S13 and capacitor C26. Switch group A and Switch group B consistof several switches controlled by external control signals, each switchserves as one output, and independent switch S12 and independent switchS13 are controlled by external control signals.

D. As shown in FIG. 11, it includes capacitor C27, capacitor C28,inductor L20, switch group C, independent switch S14 and independentswitch S15. The output end of output transformer T2 is grounded viaindependent switch S14 and capacitor C27, also, the output end of outputtransformer T2 is connected to switch group C via inductor L20, and theend of inductor L20 connected to switch group C is further grounded viaindependent switch S15 and capacitor C28. The switch group C consists ofseveral switches controlled by external control signals, and each switchserves as one output. Those switches, independent switch S14 andindependent switch S15 constituting switch group C may be independentlyarranged, or integrated on an independent SOI chip. Capacitor C27 andcapacitor C28 constitute a trap circuit, and besides capacitor C27 andcapacitor C28 described in the present application, any types of theexisting trap circuit may be used. For example, capacitor C27 andcapacitor C28 may be replaced with inductors, or inductors are connectedin series on the branches of capacitor C27 and capacitor C28respectively, to form a series circuit of capacitor+inductor.

Those switches, independent switch S12 and independent switch S13, whichconstitute switch group A and switch group B, described in A, B and Cabove, can be arranged independently, or integrated on an independentSOI chip.

The intermediate switches and change-over switches described in thepresent application can be arranged independently, or they can beintegrated on an independent SOI chip as a group of two or more switchesor all switches. For example, intermediate switch S1 and intermediateswitch S4 are a group, switch S2 and intermediate switch S3 are a group,change-over switch S5 and change-over switch S6 are a group, orintermediate switches S1-S4 are a group, or intermediate switches S1-S4,change-over switch S5 and change-over switch S6 are a group, or others.

The dual-mode power amplifier provided by the invention may adopt adistributed circuit structure, or all components can be integrated on achip by the process of bihemt/SOI/phemt/CMOS/SeGe to form an integratedcircuit. It is also possible to integrate some components on one chip,the other components on another chip, and connect the chips via signallines. For example, two or more than two or all of the intermediateswitches may be integrated as a group on an independent SOI chip. Two ormore than two or all of the change-over switches may be integrated as agroup on an independent SOI chip. The output matching circuit, inputmatching circuit, preamplifier, input transformer and output transformermay be integrated on an independent SOI chip, and each independent SOIchip is connected via a signal line.

In the present application, input transformer T1 and output transformerT2 may be any types of the existing transformer. A balanced-unbalancedtransformer (Balun) is used in the present application.

The above embodiments are only used to illustrate the technical solutionof the present application, not intended to limit it. Modifications orequivalent substitutions made by those skilled in the art, which do notdeviate from the spirit or scope of the present application, shall beincluded in the protection scope of the claims.

1. A dual-mode power amplifier with switchable working power, comprisingan input transformer, comprising a plurality of output taps, and aninput coil is loaded with a to-be-amplified signal; an outputtransformer, comprising a plurality of input taps, the number of theinput taps is matched with that of the output taps of the inputtransformer, and an output coil amplified signals; an intermediateswitch and a power-amplifier transistor, the plurality of output taps ofthe input transformer are connected with the input taps of the outputtransformer via the intermediate switch and the power-amplifiertransistor, the intermediate switch is configured with a control signalto conduct the power-amplifier transistor connected in series with theintermediate switch, so that one or more of the output taps of the inputtransformer are communicated with the input taps of the outputtransformer, and an amplified signal is output after being transformedby the output transformer; and a first matching capacitor and a secondmatching capacitor, the first matching capacitor and the second matchingcapacitor are connected in parallel between taps at both ends of theinput coil of the output transformer and ground.
 2. The dual-mode poweramplifier with switchable working power of claim 1, wherein achange-over switch is connected between taps at both ends of the inputcoil of the output transformer and the first matching capacitor.
 3. Thedual-mode power amplifier with switchable working power of claim 2,wherein two or more of the intermediate switches and the change-overswitches are a group and integrated on a single SOI chip.
 4. Thedual-mode power amplifier with switchable working power of claim 1,wherein two or more of the intermediate switches are a group andintegrated on a single SOI chip.
 5. The dual-mode power amplifier withswitchable working power of claim 1, further comprising an inputmatching circuit and a preamplifier, wherein the to-be-amplified signalloaded on the input coil of the input transformer is matched by theinput matching circuit and amplified by the preamplifier and thenloaded.
 6. The dual-mode power amplifier with switchable operating powerof claim 5, wherein the input matching circuit comprises an input filtercircuit.
 7. The dual-mode power amplifier with switchable working powerof claim 1, further comprising an output matching circuit, wherein theamplified signal output by the output coil of the output transformer isoutput after passing through the output matching circuit.
 8. Thedual-mode power amplifier with switchable working power of claim 7,wherein the output matching circuit comprises an output filter circuitand a switch group, and the amplified signal output by the output coilof the output transformer is filtered by the output filter circuit, thenloaded on the switch group and output via the switch group.
 9. Thedual-mode power amplifier with switchable working power of claim 1,further comprising a selection circuit mainly composed of a selectionswitch S and a capacitor C, and the selection circuit is connected inseries between taps at both ends of the input coil of the outputtransformer.
 10. A mode switch method of the dual-mode power amplifierwith switchable working power of claim 1, wherein the to-be-amplifiedsignal is loaded on the input coil of the input transformer, and acontrol signal is loaded on the intermediate switches to turn on part ofthe intermediate switches, and the power-amplifier transistor connectedin series with the turned-on intermediate switches is turned on so thatone or more of the plurality of output taps of the input transformeris/are communicated with the input taps of the output transformer, andan amplified signal is output after being transformed by the outputtransformer.